FILM REVIEW; A Hangover Is the Least of His Problems

Most of the meager charms of the chaotic romantic farce ''A Guy Thing'' spring from the deft comic contortions of Hollywood's ultimate nerdy sidekick, Jason Lee. As Paul Morse, a Seattle ad salesman about to marry his boss's daughter, Karen (Selma Blair), this 32-year-old actor expands from the blandly goofy Keanu-manqué he often plays into a variation on the comic leading man Ben Stiller has made into a specialty.

But while Mr. Stiller's neurotic alter egos crackle with a frizzy-haired, whiz-kid sensitivity, Mr. Lee's beleaguered man-child dons a self-protective mask of boyish naïveté. Behind his calculated blankness you sense the sly amusement of an inveterate prankster getting away with mischief. His character in ''A Guy Thing'' survives a succession of physical and psychic humiliations brought on by his own cowardice to emerge battered but with his dignity reasonably intact. But even if he's an inch or two closer to maturity, it remains miles out of reach.

Paul's troubles begin the morning after his bachelor party (six days before the wedding), when his future mother-in-law telephones to announce that his fiancée is on her way over to his house. Gazing across the bed, he discovers a strange young woman lying on the next pillow. The beautiful stranger, Becky (Julia Stiles), is none too pleased when Paul abruptly shoos her out of his apartment before she can retrieve her underwear, which he discovers in the nick of time, allowing him to hide it inside his toilet tank. (Not to worry; that underwear makes a dramatically soggy reappearance late in the film.)

Things worsen when Paul discovers in the middle of a business presentation that he has an acute case of crabs and goes into a scratching fit. His embarrassment is compounded at the drug store, where he runs into his future mother-in-law while buying delousing medication and tries to cover up his mission by enlisting the pharmacist in an animated discussion of crabmeat recipes. (Yes, the jokes are that idiotic.)

Adding to Paul's anxiety, Becky keeps popping up everywhere he turns. And when it emerges that she is also Karen's cousin, he flies into a panic. But even after Becky assures Paul of her silence and that, in any case, nothing happened between them, he remains so fearful of Karen's wrath that he keeps piling on lies.

The movie becomes so desperate for adrenaline that it throws Paul another nasty curve by having him stalked by Becky's crazy ex-boyfriend, Ray (Lochlyn Munro), a sadistic, muscle-bound cop who likes to flex his pectorals in the mirror and crow, ''Well, hello, fellas.'' Eventually, Becky and Paul find themselves cringing behind the glass doors of Ray's bathtub as his guard dog lunges at them. How and why did they land there? It's not worth asking.

''A Guy Thing,'' which opens nationwide today, was adapted from a story by Greg Glienna, one of the writers of ''Meet the Parents,'' and much of it plays like a confused, desperate rehash of that hit comedy starring Robert De Niro and Mr. Stiller. Once again, an insecure young man has to run a humiliating obstacle course to please an intimidating future father-in-law, but this time that dad, Ken (James Brolin), is not the leading character. With his gleaming, gunmetal coif and eyes narrowed into the bullying squint of a drill instructor, Mr. Brolin clearly relishes his caricature of a macho chief executive who rationalizes questionable male behavior with four words: ''We're men, we're hunters.''

''A Guy Thing,'' directed by Chris Koch, lives up to its title in its haphazard treatment of its women. Ms. Blair's one-note fiancée is nothing more than a walking danger signal. And the dull, underwritten role of Becky is an unfortunate misstep for Ms. Stiles, a serious actress from whom comedy does not seem to flow naturally. Applying her best Jane Fonda voice to the zany, free-spirited Becky, Ms. Stiles sounds matter-of-fact when she should sparkle.

As Becky and Paul grow to realize that they're made for each other, the story presents her as liberating him into a more adventurous, easygoing way of life. But what does that really mean? Paul's inner daredevil is supposedly unleashed when she takes him on a high-speed car ride through a hilly section of the city, and he decides to sit back and enjoy the ride. Some liberation!

Directed by Chris Koch; written by Greg Glienna, Pete Schwaba, Matt Tarses and Bill Wrubel, based on a story by Mr. Glienna; director of photography, Robbie Greenberg; edited by David Moritz; music by Mark Mothersbaugh; production designer, Dan Davis; produced by David Ladd and David Nicksay; released by Metro-Goldwyn-Mayer Pictures. Running time: 97 minutes. This film is rated PG-13.